There is a way.
1. Insert a very small jpeg using the drawing tool. Call it "last page subset 1"
duplicate it and call subsequent copies "last page subset 2" etc (custom name in the drawing settings)
note : use a jpeg or something that does not require a view to be saved, else it could be deleted
2. Create a master for each subset - of course they can be identical, set an auto-text reference to last page subset 1 and use the auto-text category for "last page subset one" . Then place that jpeg on the last page of the subset.
3. Repeat for each subset
In a flat folder system (no subsets) this can be handy for showing say 10 pages when the layout book has a total more than 10.
note that in the attached jpeg, the master shows 7 layouts but the subset has 8
Ben